Computing car locations in a train

ABSTRACT

A novel method and apparatus is disclosed for measuring the successive distances between the wheels of cars in a train and processing said measurements to locate a given axle of a car, such as the first axle of a truck of a car or the first axle of the car.

lliiiied Slates ateni [191 @anliler Q11 al.

MslMarch 20, 1973 [54] CGMPUTKNG CAR LOCATIONS IN A TRAHN [75]lnventorsz Paul W. Caulier, Greenwood; Donald W. Greene, Fishersville,both of Va.

[63] Continuation-impart of Ser. No. 14,574, Feb. 26,

- I970, Pat. NO. 3,646,343.

[56] References Cited UNITED STATES PATENTS 3,500,039 3/1970 Kortyna..246/77 Primary Examiner-Robert G. Sheridan Assistant ExaminerGeorge H.Libman Attorney-Amold E. Renner et al.

[ 5 7 ABSTRACT A novel method and apparatus is disclosed for measuringthe successive distances between the wheels of cars in a train andprocessing said measurements to [52] US. Cl. 246/247, 177/163, 246/77locate a given axle of a car, such as the first axle of a [51] Hm. Cl...B61l 1/16, G06f 7/02 truck of a car or the first axle of the car [58]Field of Search ...246/77, 247; 340/23; 177/163,

177/DlG. 8 8 Claims, 7 Drawing Figures -:'f c": Q-D D +iD +'4-D -+D -+D+D +0 +D +o +D n +o,

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PATENTEUHARZOIQYS SHEET 2 [IF 3 H wm vm M H/ mm mm; mN M 73 N m a O i QMWt Y i Y T X i Y Y x T i PATENTEUHARZOISH 7 1, 20

SHEET 30F 3 CLOCK REGISTER A COUNT COUNT CONTROL RESET TRANSFER REGISTERB RESET IJO SUBTRACTER TRANSFER\\ REGISTER C RESET OUTPUT PULSEINDIGATING S TART OF LOOP ON WHEEL PULSE PARALLEL TRANSFER (-A) TO (B)COUNT CLOCK PULSES INTO (A) AND (B) UNTIL NEXT WHEEL PULSE-STOP COUNTINGAND LOOP ON WHEEL PULSE -l4,574 filed Feb. 26,

l COMPUTING CAR LOCATHONS llN A TRAIN This is a continuation-in-part ofapplication Ser. No. 1970, now U.S. Pat. No.: 3,646,343 issued Feb. 29,1972.

BACKGROUND OF THE INVENTION This invention relates to arrangements foridentifying the passage of the wheels of a train of cars and particu-'larly to methods and apparatus for identifying the passage of the firstwheel of a truck or the first of a car in the train.

The need for such method or apparatus .finds a primary application inconnection with apparatus for detecting hot journal bearings, that is,hot boxes on a passengerrailroad train. In a separate application, Ser.No. 14,574, filed Feb. 26, 1970 in the names of Paul W. Caulier andDonald W. Greene, and assigned to a common assignee, of which this is acontinuation-in-part application, the background of hot box detection.is described in detail and an improved method and apparatus claimed foridentifying hot boxes with great accuracy and high reliability.

Typically, hot b ox detectors comprise a heat sensor such as athermocouple or thermocell disposed at a track site along both sides ofthe rail. Such detectors have a sighting axis which intersects thepassing journal boxes such that the heat generated therein can bemonitored. Ideally, each sensor serves to detect the heat generated bythe individual passing journal box. Thus, each box as it passes thedetector generates a signal having an amplitude proportional to thetemperature rise of that box with respect to some reference value. Thepreviously mentioned application describes an improved arrangement forevaluating heat signals to indicate the presence of a hot box. To detecthot boxes, separate sensors are provided for each train side. An averagetemperature value for each side of the passing car is derived from thesensed or monitored temperatures. Comparison is then effected betweenthe temperatures of the individual journal boxes disposed on a given carside and any deviations above predetermined limits are utilized tosignify the presence of an alarm condition.

After the presence of a hot box condition has been accurately detectedand reliably evaluated, any alarm condition must still be correlated toa particular car and wheeLThe typical prior-art system, however, islargely inadequate in this respect as such systems nor-- mally areoperative only to indicate the number or count of the axle from eitherthe front or the rear of the train at which a hot box exits. Thus, oncean alarm condition is detected and the axle information given to thetrain crew, the train must be stopped and the train crew must walk tothe car at which the hot box exists, counting axles along the way fromeither the front or "the rear of the train. Since a manual counting ofaxles must actually be effected in many of the prior-art techniques,counting errors are easily possible andthus the overall adequacy of thehot box detecting systems is markedly reduced.

In summary, then, the prior-art techniques are deemed deficient asconcerns the actual evaluation of hot boxes and identification of anydefective cars.

SUMMARY OF THE INVENTION A need thus exists in the art for an improvedmethod and apparatus for identifying the passage of the wheel axles ofthe cars of a train. It is the primary object of the instant inventionto provide such a method and apparatus which satisfies this need.

Further, more specific yet equally important objects of the instantinvention concern:

a. Providing an improved measurement method and apparatus.

b. Providing a novel method and apparatus wherein wheel axles areidentified from measurements of the distances between passing wheels.

c. Providing improved wheel identification of the passing cars in atrain.

These objects, as well as other objects which will become apparent asthe description proceeds, are implemented by the novel invention-which,from a broad standpoint, will be seen to comprise both a novel methodand apparatus for locating the wheels of the passing cars in a train.

In accordance with the novel invention concepts, there is provided anarrangement for detecting the passage of a train of cars moving past agiven point wherein each car comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels, said arrangementcomprising the steps of measuring the distance between successive wheelsof the car in said train in response to the passage of the wheels past agiven point; providing a first signal representative of the passage ofthe first axle of each truck comprising subtracting each measureddistance from the preceding measured distance and generating said firstsignal in response to the value of each subtraction having a given, onepolarity; and providing a second signal representative of the passage ofthe first axle of a car preceding first signal and generating saidsecond signal in respcinse to the value of each subtraction having agiven polarity opposite to said one polarity.

The novel invention further includes a means for corfrelating thepresence of an alarm condition signifying a detected hot box, with aparticular car and wheel, this correlation also being effected in acompletely automatic fashion. In this respect, the novel inventionincorporates means which serve to detect either the center or the end ofa passing car and to generate a car signal in response thereto. Thissignal is utilized to effect various transfer operations of theindividual heat signals derived from the passing journal boxes of thecar in a fashion to be discussed in more detail hereinbelow.

In the preferred inventive embodiment, the hot box information, i.e.,the presence of an alarm condition and the particular car, wheel andside at which the alarm condition has occurred, is then forwarded orenunciated to the train crew and preferably to the engineer of the trainsuch that the train crew can readily correct the defective conditionsand keep the down time of the train at a minimum.

BRIEF DESCRIPTION OF THE DRAWINGS The invention itself will be betterunderstood and further features and advantages thereof will becomeapparent from the following detailed description of a preferredinventive embodiment, such description making reference to the annexeddrawings, wherein:

FIG. 1 is a functional block diagram schematically representing thenovel hot box detection system of the aforementioned parent application;

FIG. 2 is a schematic block diagram illustrative of the remote readoutdevice utilized with the novel not box detection system ofthe parentapplication;

FIGS. 3a, 3b, and 3c are schematic representations of a digitaltechnique utilized to detect individual cars of an average signal from aplurality of wheels on one side of each car, and preferably from allwheels at one side of each car, and to compare each individual wheel ofthat car side in a suitable manner to the derived average signal value.In this fashion, a comparison can be utilized, such as a ratiocomparison, for obtaining a result which is nearly independent of allvariables and thus the detector output would, in effect, be a reliablecriterium of the presence of an alarm condition.

Expressed mathematically,,it can be seen that the ratio output of thedetecting apparatus equals:

the passing train so as to correlate individual wheel signals withparticular cars.

FIG. 4 is a functional block diagram of a novel car detector apparatusutilized with the overall hot box detection system of the invention; and

FIG. 4a is a flow diagram of how the car detector logic operates.

DETAILED DESCRIPTION OF A PREFERRED INVENTIVE EMBODIMENT The presentinvention finds particular application in conjunction with the system ofthe previously identified US. Pat. No. 3,646,343 which comprises atechnique wherein an average temperature signal is derived from aplurality of journal boxes disposed on one side of each car, and thesignal individual to each journal box of that car side is compared tothe average signal value. This technique in and of itself represents atotally new approach in the art of autoinatic evaluation and, as hasbeen alleged, serves to effectively eliminate all noncritical sidedependent variables from the actual heat monitoring of the passingjournal boxes. Now, it should be understood that a hot box sensor ordetector will produce a heat signal for each wheel, the value of suchsignal depending upon the number of parameters.

For example, the output of the sensors of the novel detector system canbe shown to depend upon (1) the heat absorption from external sourcessuch as the sun f(a) (2); a heating due to motion or speed of the carf(v); (3) a heating due to loading of the carf(v); (3) a heating due toloading of the car f(L); (4) the bearing heating factor f,, whichincreases when a hot box develops; (5) the heat loss into the side frameof the truck f(h); (6) the heat-loss due to winds unrelated to trainmotion f(W); (7) the heat loss due to drive wind f(V 8) the changes inbearing position relative to the hot box detector caused by changes inwheel size f(P); (9) the changes due to view or line of sight adjustmentof the scanner f(A); (10) the changes due to attenuation of the opticalpath due to dust, dirt, snow, etc.f(g); (11) the changes due to the gainof the detector unit f(G); (l2) and the changes due to variation in thedetector frequency response f(S).

Now, it should be understood that the heat absorp tion from externalsources f(a), the heating due to loading f(L), the heating loss due towinds unrelated to train motion, such as cross winds, f(W), the changesdue to the adjustment and line of sight of the scanner f(A), the changesdue to variations in the detector frequency response are all variableswhich primarily depend upon and are functionally related to one or theother of the two car sides. Thus, it is desirable to derive assumingthat only f(b) varies significantly between normal and hot bearings.Now, this expression reduces =fl(b)'n/fl(b)+. .+fn(b) making thejustified assumption that the quantity is small compared to the quantity1/n [f(v)+f(L)](fl(b) .+fn(b)) The detector output will be 1 if the onewheel signal f (b) equals the average wheel signal. In the previousequations, n number of axles of one car and f (b) factorf of the firstwheel of one car side.

An examination of equation (1) verified that each heat signal depends onvariables which are unique for that train side and that sensor.

Comparing one such heat signal to the average of one car side anddividing by the average produces equation (2), after standardmathematical manipulations. It is significant that all the sidedependent factors f(P),f(A), f(g),f(G) and f(S) vanished from theequation. This is the advantage of taking a ratio although othercomparison techniques can also be used.

Equation (2) now is the mathematical expression of the alarm criteriumof the novel inventive technique when comparing one heat signal (ofbearing Al) to the average of that train side.

Expressed in a different fashion, the novel technique of this system issuch that the temperature t, of each of a plurality n journal boxesdisposed on one side of a car is monitored to obtain a plurality ofseparate quantities t, (x=l .n). Then, the quantity X=ll A 1/! 1.1"

is obtained. If a ratio comparison is desired, separate quantities arethen obtained, B t,//\ where (x=l n) and, each quantity B, is thencompared with a reference or limit quantity and an alarm is selectivelygenerated in dependence upon this comparison. An alternative method ofcomparison, where division is expensive or slow, is to determine thedifference between each wheel temperature and the average temperature ofall wheels (or given plurality of wheels) on the same side of the samecar. This temperature difference may be represented by the followingexpression:

From an apparatus standpoint, this technique is effected by providing asensor means which is responsive to the temperature of the journal boxeson the cars of a passing train. The sensor means is contemplated to feedinto an evaluator means which is coupled thereto for producing an outputwhich would be representative of the comparison made between thetemperature of a journal box on a given side of a car and the averagetemperature value of all journal boxes disposed on the given car side,such comparison preferably being of the ratio type although othercomparison techniques are also suitable. Finally, comparison means wouldbe provided for comparing the evaluator output with a reference or limitvalue and for selectively producing an alarm indication therefrom.

Referring specifically now to FIG. 1 of the drawings, the actual tracksite equipment contemplated to be utilized with the novel inventivesystem is depicted. A typical railroad track is designated by referencenumeral and, to either side of the railroad track, sensing units 12 aredisposed. These sensing units are contemplated to comprise infrared heatdetectors having a sight axis intersecting the journal boxes of apassing train.

Now, as each journal box of the passing train goes by the associatedsensor 12 disposed to either the right or the left of the track 10 atdesired locations to properly view the passing journal as indicated bythe wheel sensor indicating wheel passage, sensors 12 respectively serveto generate an analog voltage signal on lines 14 and 16, the value ofthis signal being proportional to the magnitude of the heat actuallysensed. At the same time, as each axle or wheel goes by, a pulse isproduced by a wheel sensor 1% on line 20.'Heat sensors 12 and wheelsensor 18 form a conventional hot box detector unit generally designated22 such as the General Electric Hot Box Detector Model 3875 l6HB.

The analog voltage signals on lines 14 and 16 proportional to the heatof the journal boxes to either side of a single passing axle form theinput to a heat signal digitizer 23 which serves to convert the analogvoltage signals from each of the sensors 12 into digital signalspreferably of a binary nature. The analog-to-digital conversion withinthe heat signal digitizer 23 takes place in synchronism with the wheelpulse generated on line Zll and input as a gating signal into the heatsignal digitizer 23 via line 24. In the preferred inventive embodiment,the heat signal digitizer 23 comprises a conventional gatedanalog-to-digital converter and incorporates two channels for the rightand left heat signals generated on lines 14 and 16, respectively, by theheat sensors l2.

As each axle or wheel of the car passes by the hot box detector 22, therespective analog voltage signals generated and converted into digitalsignals are then serially discharged into a holding storage means 3t)along lines 26 and 28. Again, in the preferred inventive embodiment,holding storage means 30 preferably comprises two separate storagedevices such as shift registers so that the heat signal from the rightside of the car and the heat signal from the left side of the carrespectively carried along lines 26 and 2d are maintained separately. Ifdesired, however, and as should be apparent to those skilled in the art,a single output channel could be provided and the right and left heatsignals separated on a serial time sharing basis. Holding storage means30 thus, at any one time, will contain a plurality of digital signalsrepresentative of the journal box heat of a number of axles that havepassed by the hot box detector 22.

In accordance with the novel invention, the digital heat signals storedin the holding storage means 30 are correlated with a particular carthat has passed by the heat detector 22. This correlation must takeplace since, as described at the outset of the specification, the novelinventive method and apparatus essentially serves to analyze the heatsignals generated by each respective car and furthermore, serves toseparately analyze the heat signals generated by the journal boxesdisposed on each side of the respective car. Thus, a car detector means32 is provided into which the wheel or axle pulses from wheel counter 18are fed via lines 20 and 34. The output of the car detector means 32 iscontemplated to comprise a gating pulse on line 36 representative of thepassing of a single car, this gating pulse serving as a transfer signalfor the holding storage means 30. In this fashion, a plurality ofdigital heat signals equal to the number of journal boxes disposed on arespective car are stored in the holding storage means 30 and, upon thepresence of the transfer signal from car detector means 32 via line 36,the plurality of stored signals are then subsequently analyzed in afashion to be described hereinbelow. The process serves to repeat itselfas will be apparent on a car-bycar basis.

The car detector means 32 and particularly its functional operation inand of itself constitutes a novel and advantageous approach in the art.It is for this reason that it would be useful at this point to digressfrom the description of the overall system and to describe in moredetail the structure and operation of the car detector means 32. In thisrespect, attention is directed to FIG. 3 of the drawings from which thenovel operation of the car detector means 32 can be understood.

in FIG. 3, a plurality of railroad cars are designated by referencenumerals 38, 40 and 42, respectively. As shown, each car is seen toinclude two trucks, cars 38 and 42 utilizing two-axle trucks 44 and 44',and 46 and 46, respectively. On the other hand, car 40 is seen toutilize three-axle trucks 48 and 48'. Thus, cars 38 and 42 each includefour wheels to a side while car 40 in cludes six wheels to a side. Now,D1 depicts the distance between axles of the same truck on each car, D2depicts the distance between the last wheel of the first truck and thefirst wheel of the second truck on each car, and, D3 depicts thedistance between the last wheel of one car and the first wheel of thenext adjacent car. For a given combination of cars and adln thefollowing discussion using distances it should be understood that atsubstantially constant speed, the respective time measurement values maybe used.

These various distances are depicted on chart 3a as upwardly directedlines 50 through 74, the magnitude or length of these lines beingrepresentative of the various distances D1, D2, D3. Thus, line 50, forexample, illustratively depicts the value of distance D1 between theaxles of truck 44 of car 38.

Referring now to chart 3b, a plurality of schematically representedlines 76 through 98 are illustrated. Each of these lines arerepresentative of the mathe-- matical difference between adjacentdistances as depicted by the lines on chart 3a. Thus, for example, line76 on chart 3b has a value representative of the difference between line52 and line 50 on the chart 3a, or the value of line 52 minus the valueof line 50. Similarly, line 78 on chart 3b has a value, negative in thiscase, representative of the value of line 54 minus the value of line 52in chart 3a. Similarly, line 86 in chart 3b represents the value of line62 from which the value of line 60 has been subtracted on chart 3a.

Going one step further and referring now specifically to chart 3c, thelines thereon depict the values obtained by taking the differencesbetween only the positive or upwardly directed lines 76, 80, 86, 92 and96 of chart 3b. Thus, the value of line 100 which extends downwardly andthus, by convention, is negative, represents the value of line 80 fromwhich the value of line 76 in chart 3b has been subtracted. Line 102represents the value of line 86 from which the value of line 80 has beensubtracted. Line 104 represents the value of line 92 from which thevalue of line 86 has been subtracted. Finally, line 106 represents thevalue of line 96 from which the value of line 92 has been subtracted.

Now, as should be apparent, it will be noted that all positive values,i.e., 102 and 106, obtained on chart 3b, represent the first wheel ofthe last truck of each car. Similarly, all negative values 100 and 104of chart 30 represent the first wheel'of the first truck on each car.Accordingly, by merely taking the negative values, for example, one lineis obtained for each car and this line is representative of the outputgenerated by the car detector means 32. Each negative value signal isthen used to initiate computation of data accumulated during passage ofthe previous car. The positive value pulses are ignored.

To summarize the above concept, the distances between the various wheelsof the passing cars are plotted and the differences between a givendistance and the preceding one are taken so as to obtain eitherpositive, negative or zero values in synchronism .with the measurementof the given distance. Now, only the positive values (i.e., 76, 80, 84,86 of FIG. 3b) thus obtained are next considered. Specifically, thedifferences between each positive value and the preceding value aretaken and, from such differences, positive and negative values (see FIG.30) are obtained. Importantly, however, only a single positive and asingle negative value are obtained and at a specified location on thecar. Thus, by monitoring negative values, for example, one signal willbe produced upon the passage of each car of the train, this signal being.utilized as a transfer or gating signal, as discussed. As a check toinsure proper operation of the wheel detector, i.e., to recognize missedwheels, the output of the car detecting means 32 is monitored to assurethat only even numbers of axles per car and cars with at least'fouraxles are recognized. I

Car detector monitor, which may comprise a counter, responds to thesignals, i.e., wheel pulses, over 20 to count up the number of axlessensed at the indication of the end of car signal on 36, the numberstored in the counter indicates whether the number of axles counted isodd or exceeds a given number such as eight axles. If such a faultindication is produced, a signal is transmitted over 41 to holdingstorage circuit 30 to block transmission of signals from 30 to 130 and136 and to apply signals to 156 to actuate comparator 156 to perform thealternate temperature algorithm to be described.

The car detector is shown in more detail in FIG. 4. It will be seen thatthis is composed of three registers A, B and C, a clock and a countcontrol circuit together with a system control circuit. An additionalsubtracter BC is shown with an output connected through an output gateto be described later. The wheel signal 34 feeds into the signal controlbox as indicated. Before the first wheel signal is received, the threeregisters A, B and C are reset to zero. When the first wheel signal isreceived, the system control through the count control starts countingclock pulses into the register A. At the same time clock pulses arecounted into the register B. When the second wheel signal is received,the counting into the A and B registers is temporarily halted and thefollowing procedure takes place. The contents of the B register areexamined to determine if it is positive. If it is positive, the contentsof the C register are subtracted from the contents of the B register bythe subtracter labeled BC. Since zero was initially loaded into the Cregister, the results of such a subtraction must be positive. Under thiscondition, there will be no output to the output gate leading to line36. Since the contents remaining in the B register were positive, theresults will be transferred to the C register. The number in the Bregister will now be erased and the negative of the quantity in the Aregister will be transferred to the B register. The count controlcircuit is now implemented and clock pulses are counted in the Aregister until the next wheel signal. During this time, both the A andthe B registers are counted up. On the next wheel signal, the countprocedure is stopped and the following procedure is stared.

First the contents of the B register are examined to determine whetherthe result is negative or positive; If it is negative, the negative ofthe number in the A register is transferred to the B register and thecount continues without altering the C register. If, however, the Bregister indicates a positive BC the BC subtracter must perform theindicated BC subtraction to determine the polarity of the result. Again,if the result is positive, there is no output but if it is negative, anindication is transmitted to indicate the beginning of a car over lead36. At the end of this time, the contents of the B register aretransferred to the C register and the negative of the A register istransferred to the B register and the count is resumed for the nextintegral. This procedure is repeated for each subsequent integralbetween successive wheel signals.

Referring again now to the overall system of FIG. 1, it has been seenthat the output from the car detector means 32 on' line 36 comprises onepulse, for example such as or 104 of FIG. 30, per each passing car and,as explained above, this pulse serves as a transfer or .into a sideaverager means 130 wherein an average signal value for the individualheat signals of the car side is obtained and is output on line 132. Eachof the individual heat signals for this particular side is then outputonce again from the holding storage means along line 136. One by one,the individual heat signals on line 136 are compared with the averageside signal value on line 132 in a signal comparator means 138. Anydeviation of an individual heat signal from the average heat signal forthat side that does not fall within predetermined, preset limitsfunctionally designated by block 140, causes an output to occur on line142 into an alarm output means 144. At the same time the output of carcounter 42, car side monitor 43 and axle counter 44 are communicated toalarm output 144 to indicate the location of the hot box. At the sametime,

the actual average side value from the side averager means 130 is inputvia line 146 into an average comparator means 148. If the value of atleast one right-side average signal and one left-side average signalavailable from 130 exceeds a predetermined limit as set, no heatdetector malfunction signal will be transmitted over lead 163 to soundan alarm by 144 at the end of the train as indicated by the terminationof wheel signals as indicated on line 34. If, however, either side failsto produce such a signal, a malfunction indication will be given. Suchmalfunctions as would typically affect the average comparison value aremissing heat or wheel signals, system gain, and the like. As discussedabove, the ability of the novel system to monitor its own operation inthis fashion assures confidence in the veracity of its alarm indication,as a checking alarm output would otherwise occur.

After the heat signals from the right side of the individual passingcarhave been analyzed in this fashion, all heat signals stored in theholding storage means 30 for the left side of the car are then acteddigital in the same manner and the value of the average left-side signalfrom the side averager means 130 is also compared in the averagecomparator means 148 to predetermined limits 150 to determineoperability of the detecting device. Subsequently, a further set ofdigitized heat signals would be dumped from the heat ,signal digitizermeans .23 into the holding storage means 30, this set of heat signalsbeing those obtained from the next succeeding passing car. As will berecognized, the signal comparator means 138, the side averager means130, and the average comparator means 148 may comprise conventionaldigital logic components.

So as to further increase the operational reliability of the novel hotbox detector system, provisions are made for obtaining an alarm outputsignal in the event that, through malfunction, the synchronizing andtransfer signal from the car detector means 32 does not occur. In thisrespect, an auxiliary axle comparator means 156 is redundantly"provided, this comparator means 156 being in accordance with any typicalprior-art construction whereby the difference or ratio of two successivedigital signals are compared. Specifically, in the event of amalfunction of car detector means 32, digital heat signalsrepresentative of the temperature of the journal boxes on both the rightand the left side of the same axle are successively output from theholding storage means 30 into the auxiliary axle comparator means 156via line 158 wherein the ratio or difference of the signals is taken andwherein an alarm condition output is transferred via line 160 into thealarm output means 144 in the event of deviations of thecomparisonresult from any preset limits. In this sense, then, theredundant portion of the novel hot box detector system of the instantinvention serves to automatically switch from its preferred operationinto the operation of prior-art detector systems.

Many different modes of transferring this alarm" information to thetrain crew can be utilized within the overall inventive conceptsexpressed herein. For example, this information can be transmitted overconventional lines to a train dispatchers office, the train dispatcherreading the information and operating certain trackside signals visuallyobserved by the engineer of the train at some distance down the track.

A particular form of transferring alarm indicia to the train crew ispreferred, however, and is described hereinbelow. The alarm output means144 would serve to store the input alarm information and, when the trainhas passed by the track site location of hot box detector 22, wouldserve to transmit a sequential coded radio message over a schematicallyindicated transmission path 160 to a remote readout or printout means162 actually carried on board the train, such remote readout meanscomprising a receiver and a display device. The sequential coded messagetransmitted by the alarm output means 144 is contemplated to contain thefollowing information:

Start Code; Total Number of Wheels; Hot Box at Wheel No. (right or left)side, car

Number: Hot Box at Wheel No. (right or left) side, car

Number: ,etc.:; Detector (in or out of) order; and Code.

This sequential code is contemplated to be trans- In the event ofmalfunction of the car detector means 32, information as to the carnumber at which an alarm has occurred cannot be transmitted to theremote readout means 162. Rather, the output of the auxiliary axlecomparator means 156 and thus the transmitted output of the alarm outputmeans 144 would merely give the axle number from the front of the train,for example, at which an alarm condition has occurred. With only thisinformation, the train crew would have to manually count axles to thedefective location.

As should now be apparent, the objects initially set forth at the outsetof this specification have been successfully achieved.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A method of detecting the passage of a train of cars moving pastagiven point wherein each car comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels, said methodcomprising the steps of:

measuring the distance between successive wheels of the car in saidtrain in response to the passage of the wheels past a given point;providing a first signal representative of the passage of the first axleof each truck comprising subtracting each measured distance from thepreceding measured distance and generating said first signal in responseto the value of each subtraction having a given, one polarity;

and providing a second signal representative of the passage of the firstaxle of a car comprising subtracting each said first signal from thepreceding first signal and generating said second signal in response tothe value of each subtraction having a given polarity opposite to saidone polarity. 2. A method of detecting the passage of a plurality ofcars moving past a given point wherein each car comprises a plurality oftrucks with each truck comprising a plurality of axle bearing wheels,said method comprising the steps of:

measuring the distance between successive wheels of the cars in responseto the passage of the wheels past said given point; 7

providing a first signal representative of the passage of the first axleof the truck comprising comparing each measured distance with thepreceding measured distance and generating said first signal in responseto the value of each comparison exceeding a given value in a firstdirection; and providing a second signal representative of the passageof the first axle of a car comprising comparing each said first signalwith the preceding first signal and generating said second signal inresponse to the value of each comparison exceeding a given value in theopposite direction. 3. A method of detecting the passage of railroadcars each comprising a plurality of trucks wherein each truck comprisesa plurality of axle bearing wheels, said method comprising the steps of:

automatically measuring the distance between successive wheels of thecars of a train in response to the passage of the wheels past a givenpoint;

electronically comparing each measured distance with the precedingmeasured distance and'generating a first signal representative of thevalue of each comparison only when it has a given polarity;

electronically comparing each first signal with the preceding firstsignal and generating a second signal representative of the value ofeach said lastnamed comparison only when it has a given polarity.

4. Apparatus for detecting the passage of a train of cars moving past agiven point wherein each car comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels, said apparatuscomprlslngz means for measuring the distance between successive wheelsof the car in said train in response to the passage of the wheels past agiven point;

means for subtracting each measured distance from the preceding measureddistance and generating a first signal representative of the value ofeach subtraction, means only responsive to each first signal having agiven, one polarity for providing a first output signal representativeof the passage of the first axle of a truck; means for subtracting eachsaid first signal from the preceding first signal and generating anadditional signal representative of the value of said subtraction, meansonly responsive to each such second signal having a polarity opposite tosaid given one polarity for providing a second output signalrepresentative of the passage of the first axle of a car. 5. Apparatusfor detecting the passage of a plurality of cars moving past a givenpoint wherein each car comprises a plurality of trucks with each truckcomprising a plurality of axle bearing wheels, said apparatuscomprising:

means for measuring distance between successive wheels of the cars inresponse to the passage of the wheels past said given point; means forcomparing each measured distance with the preceding measured distanceand generating a first signal representative of the value of eachcomparison, means only responsive to each first signal having a valuewhich exceeds a given value in a first direction for providing a firstoutput signal representative of the passage of the first axle ofa truck;means for comparing each said first signal with the preceding firstsignal and generating an additional signal representative of the valueof each comparison, means responsive only to each such second signalhaving a value which exceeds a given value in the opposite direction forproviding a second output signal representative of the passage of thefirst axle ofa car.

6. Apparatus for detecting the passage of railroad cars each comprisinga plurality of trucks wherein 'each truck comprises a plurality of axlebearing wheels, compnsmg:

means for automatically measuring the distance between successive wheelsof the cars of a train in response to the passage of the wheels past agiven point;

means for electronically comparing each measured distance with thepreceding measured distance and generating a signal representative ofthe value of each comparison which has a given polarity; means forelectronically comparing each said signal with the preceding signal andgenerating an additional signal representative of said comparison;

and means for generating an output signal cor-- responding to each ofsaid additional signals which has the same polarity representing thefirst wheel of the first truck of each car.

7. Apparatus for detecting the passage of a train of cars moving past agiven point wherein each car comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels comprising:

first, second and third counters,

a source of recurrent timing pulses,

means for detecting the passage of wheels past said given point,

means for enabling said first counter to count the timing pulsesoccurring between detection of the passage of a first detected wheel anda preceding wheel to provide a first count value,

means for transferring said first count value as a negative first countvalue to said second counter,

means for enabling said first and second counters to count the timingpulses occurring between detection of the passage of a second wheel andsaid first wheel to obtain a second count value and the differencebetween said second and first count values in said first and secondcounters respectively,

means responsive to said difference having a positive value fortransferring said difference as a negative difference count to saidthird counter,

means for operating said first and second counters to count the timingpulses occurring between detec tion of the passage ofa third wheel andsaid second wheel to obtain a third count and the difference betweensaid second and first counts in said first and second countersrespectively,

means operative when the difference between said third and second countsin said second counter becomes positive to operate said third counter toalso count the remainder of the count being counted into said first andsecond counters into said third counter,

and means responsive to the count in said. third counter being negativeat the end of said third count for utilizing said information.

8. An arrangement according to claim 7 further comprising meansoperative when the difference between said second and first counts isnegative for resetting said second counter to zero and transferring thenegative of said second count from the first counter into said secondcounter,

and means responsive to the total count in said third counter beingpositive at the end of the third wheel count for resetting said thirdcounter to zero and transferring the difference between said third andsecond counts as a negative difference count into said third counter.

1. A method of detecting the passage of a train of cars moving past agiven point wherein each car comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels, said methodcomprising the steps of: measuring the distance between successivewheels of the car in said train in response to the passage of the wheelspast a given point; providing a first signal representative of thepassage of the first axle of each truck comprising subtracting eachmeasured distance from the preceding measured distance and generatingsaid first signal in response to the value of each subtraction having agiven, one polarity; and providing a second signal representative of thepassage of the first axle of a car comprising subtracting each saidfirst signal from the preceding first signal and generating said secondsignal in response to the value of each subtraction having a givenpolarity opposite to said one polarity.
 2. A method of detecting thepassage of a plurality of cars moving past a given point wherein eachcar comprises a plurality of trucks with each truck comprising aplurality of axle bearing wheels, said method comprising the steps of:measuring the distance between successive wheels of the cars in responseto the passage of the wheels past said given point; providing a firstsignal representative of the passage of the first axle of the truckcomprising comparing each measured distance with the preceding measureddistance and generating said first signal in response to the value ofeach comparison exceeding a given value in a first direction; andproviding a second signal representative of the passage of the firstaxle of a car comprising comparing each said first signal with thepreceding first Signal and generating said second signal in response tothe value of each comparison exceeding a given value in the oppositedirection.
 3. A method of detecting the passage of railroad cars eachcomprising a plurality of trucks wherein each truck comprises aplurality of axle bearing wheels, said method comprising the steps of:automatically measuring the distance between successive wheels of thecars of a train in response to the passage of the wheels past a givenpoint; electronically comparing each measured distance with thepreceding measured distance and generating a first signal representativeof the value of each comparison only when it has a given polarity;electronically comparing each first signal with the preceding firstsignal and generating a second signal representative of the value ofeach said last-named comparison only when it has a given polarity. 4.Apparatus for detecting the passage of a train of cars moving past agiven point wherein each car comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels, said apparatuscomprising: means for measuring the distance between successive wheelsof the car in said train in response to the passage of the wheels past agiven point; means for subtracting each measured distance from thepreceding measured distance and generating a first signal representativeof the value of each subtraction, means only responsive to each firstsignal having a given, one polarity for providing a first output signalrepresentative of the passage of the first axle of a truck; means forsubtracting each said first signal from the preceding first signal andgenerating an additional signal representative of the value of saidsubtraction, means only responsive to each such second signal having apolarity opposite to said given one polarity for providing a secondoutput signal representative of the passage of the first axle of a car.5. Apparatus for detecting the passage of a plurality of cars movingpast a given point wherein each car comprises a plurality of trucks witheach truck comprising a plurality of axle bearing wheels, said apparatuscomprising: means for measuring distance between successive wheels ofthe cars in response to the passage of the wheels past said given point;means for comparing each measured distance with the preceding measureddistance and generating a first signal representative of the value ofeach comparison, means only responsive to each first signal having avalue which exceeds a given value in a first direction for providing afirst output signal representative of the passage of the first axle of atruck; means for comparing each said first signal with the precedingfirst signal and generating an additional signal representative of thevalue of each comparison, means responsive only to each such secondsignal having a value which exceeds a given value in the oppositedirection for providing a second output signal representative of thepassage of the first axle of a car.
 6. Apparatus for detecting thepassage of railroad cars each comprising a plurality of trucks whereineach truck comprises a plurality of axle bearing wheels, comprising:means for automatically measuring the distance between successive wheelsof the cars of a train in response to the passage of the wheels past agiven point; means for electronically comparing each measured distancewith the preceding measured distance and generating a signalrepresentative of the value of each comparison which has a givenpolarity; means for electronically comparing each said signal with thepreceding signal and generating an additional signal representative ofsaid comparison; and means for generating an output signal correspondingto each of said additional signals which has the same polarityrepresenting the first wheel of the first truck of each car. 7.Apparatus for detecting the passage of a train of cars moving past agiven point wherein each caR comprises a plurality of trucks with eachtruck comprising a plurality of axle bearing wheels comprising: first,second and third counters, a source of recurrent timing pulses, meansfor detecting the passage of wheels past said given point, means forenabling said first counter to count the timing pulses occurring betweendetection of the passage of a first detected wheel and a preceding wheelto provide a first count value, means for transferring said first countvalue as a negative first count value to said second counter, means forenabling said first and second counters to count the timing pulsesoccurring between detection of the passage of a second wheel and saidfirst wheel to obtain a second count value and the difference betweensaid second and first count values in said first and second countersrespectively, means responsive to said difference having a positivevalue for transferring said difference as a negative difference count tosaid third counter, means for operating said first and second countersto count the timing pulses occurring between detection of the passage ofa third wheel and said second wheel to obtain a third count and thedifference between said second and first counts in said first and secondcounters respectively, means operative when the difference between saidthird and second counts in said second counter becomes positive tooperate said third counter to also count the remainder of the countbeing counted into said first and second counters into said thirdcounter, and means responsive to the count in said third counter beingnegative at the end of said third count for utilizing said information.8. An arrangement according to claim 7 further comprising meansoperative when the difference between said second and first counts isnegative for resetting said second counter to zero and transferring thenegative of said second count from the first counter into said secondcounter, and means responsive to the total count in said third counterbeing positive at the end of the third wheel count for resetting saidthird counter to zero and transferring the difference between said thirdand second counts as a negative difference count into said thirdcounter.